The Complete Guide to Propylene Glycol
Propylene glycol is a substance that’s widely used in the food and cosmetics industry. For instance, it is a common ingredient in many hygiene and cosmetic products. It is also used as an additive in many foods. Food authorities in both the U.S and Europe have ruled the product as generally safe for use in the food industry.
Since this product is also used as an ingredient in the manufacture of antifreeze, it has created quite some controversy. Health concerns about the safety of consuming foods that contain propylene glycol have arisen in the recent past. There have been claims that there could be possible toxic effects.
In this article, we take an in-depth look at propylene glycol; what it is, for what reason it’s used and whether it poses any danger to our health.
What is Propylene Glycol?
Also referred to as PG, propylene glycol is the product of the third stage of a chemical reaction which begins with propene. Propene is a byproduct of fossil fuels (natural gas processing and oil refining). PG also occurs in nature as a natural byproduct of fermentation. Propylene oxide is a volatile compound. Propylene is thought to have some cancer-causing properties. In the final stage, molecules are separated through the addition of water, in a process called hydrolyzation. This process yields propylene glycol.
The compound, propylene glycol, is identified by the chemical formula C3H8O2. It is a liquid synthetic compound with water absorbent properties. It is also referred to as 1,2-propanediol. It is a diol alcohol (an organic compound) that is an odorless, tasteless and clear liquid that is also oily. When listing the product in ingredient labels or as a compound, the name propane-1,2-diol is used. Since it is used as an additive in foods, especially in the U.S, it is referred to using the E-number E1520.
There are thousands of cosmetic products that contain propylene glycol as a major ingredient as well as lots of processed food products. You will also find this product in most of the medications that you use. It helps the body to absorb other chemicals in a more efficient manner. Aside from these, it is also a key ingredient in electronic cigarettes. It serves to sweeten the taste as well as smoothening the smoke.
There has not been a shortage of confusion in research about this liquid substance. Questions have also been asked by most people on whether the product is a danger to humans or whether it is harmless like some people claim. A convincing answer to that question has so far remained elusive. According to substantial amounts of research, however, negative effects of propylene glycol rarely occur and when they do, they are normally due to ingestion of too much of the chemical.
Propylene glycol is certainly less dangerous than ethylene glycol. This is a toxic chemical compound whose usage is mainly in some household products and many types of antifreeze. This product is considered to be highly poisonous and when ingested, either by accident or purposefully, immediate medical attention is required for treatment of its toxic substances. Since ethylene glycol has a deceptively sweet taste, its presence in antifreeze has caused the deaths of many household pets that have lapped it up when it has been on the ground. Antifreeze is usually considered non-toxic when propylene glycol is used in place of ethylene glycol.
This doesn’t bring the concerns down, however. Most people still express concerns about the presence of this ingredient in antifreeze in their foods, especially since the product is used in the deicing of airplanes. This has sparked some fierce out roars in the past years. Such a case occurred when an alcoholic drink that contained illegal levels of propylene glycol was pulled off the shelves in three European countries. The confusion in the levels occurred when the manufacturer sent the formula used in North America, instead of the one used in Europe, which contains a sixth of the propylene glycol found in the American formula.
Consumers were both amazed and angry when they learned that their favorite drinks and foods may contain the chemical. The situation was made worse by its presence in common products. The association between food and propylene glycol caused a scare among many people, despite the fact that its function is just like that of salt, that is lowering the freezing point of water, and that its introduction in antifreeze products served to replace a more dangerous chemical.
The assessment of the Environmental Working Group says that the research on this substance can be considered as “fair.” On the health concerns scale, the EWG rates propylene glycol at position “3.” This means that the health concerns associated with the product are moderately low. It also designates the known issues associated with the product in the category of “allergies and immunotoxicity.” The product does not pose any dangers related to reproductive processes or cancer.
The following points are important in our discussion on propylene glycol and its toxicity:
- It’s not “bioaccumulative.” That is, when taken in normal dosage, it is broken down within the body in 48 hours, in individuals with a healthy liver and kidney. It also does not accumulate in the body over time which may lead to toxicity.
- Industrial-grade levels of this product are only found in products like paints, cushions, antifreeze, polyurethane and the like. However, the levels found in food are considered to be pharmaceutical-grade.
- In a toxicology profile, the FDA (Food and Drug Association) has pronounced the product as “generally safe.”
- The Centers for Disease Control and Prevention published a thoroughly comprehensive report in which no serious health concerns were found to be associated with propylene glycol. However, the report also states that “there were no available studies on body weight, ocular, dermal, endocrine, renal, hepatic, musculoskeletal, gastrointestinal, cardiovascular, or respiratory effects in humans as well as ocular, dermal or musculoskeletal effects in animals after they were exposed orally to propylene glycol. Similar sentiments were shared about inhalation exposure and skin exposure. Rats, monkeys or horses were the test subjects of the research that was used to certify the safety of the chemical. Most of the points were also made based on a study that was conducted six decades ago on monkeys.
The top three points of the study are somewhat encouraging to some extent. Although propylene glycol doesn’t occur naturally in nature, it has been deemed as a safe product. The major concern on my side is what is not found – even the least bit of extensive research on how safe the product is on humans.
Let’s have an in-depth look at the current research and what it says on the effects of propylene glycol:
How Is It Used?
Propylene glycol is mainly used as an additive that aids in processing foods and improving their flavor shelf-life, appearance, and texture.
Propylene glycol is used in the following ways in foods:
Anti-Caking Agent. It helps to prevent sticking of food substances and the formation of clumps. For instance, in grated cheese or in dried soups.
Antioxidant. It protects foods from deterioration that’s caused by oxygen and hence extending their shelf life.
Carrier: It dissolves some food additives and nutrients that are used in processing, like colors, antioxidants, and flavors.
Dough Strengthener. It makes the dough more stable by modifying starches and gluten.
Emulsifier. it prevents separation of food ingredients. For instance, vinegar and oil in salad dressing.
Moisture Preserver. It prevents the drying out of foods by maintaining a stable moisture level. Such foods include nuts, coconut flakes, and marshmallows.
Processing Aid. It’s used to make food more appealing to its consumers or increase its usage among the population. For instance, making a liquid clearer.
Stabilizer and Thickener. It can also be used to thicken food components or to hold them together during processing and also after processing.
Texturizer. It changes how the food feels when in the mouth or its appearance to the eyes.
Some of the products that contain propylene glycol include dairy products, bread, fast foods, food coloring, popcorn, soft drinks, make, dried soups, dressings, drink mixes and many other packaged foods.
It is also used in hospitals in some medications that are ingested via injection such as lorazepam. Some ointments and creams that are applied to the skin also contain this product. Corticosteroids are a good example.
Since the product has chemical properties, it is not uncommon to find it in a wide range of cosmetic and hygiene products.
Is Propylene Glycol Dangerous in Foods?
The U.S Food and Drug Administration recognizes propylene glycol as a GRAS (generally recognized as safe.) product.
It’s used as an indirect and direct food additive in the US, while in Europe its use is limited to being a solvent for enzymes, antioxidants, colors, and emulsifiers. The weight limit in the final product is limited to up to 0.45 grams per pound or 1 gr per kg.
According to the world health organization, the safe amount of propylene glycol daily intake is 11.4 mg per pound of your body weight. This translates into 25 milligrams per kg. Daily ingestion of the chemical compound in the US is, however, higher than the recommended amount.
When compared, a patient who manifested toxicity symptoms used to receive a daily intake of 213 grams of propylene glycol. This amount exceeds what is available in the daily diet of a 60-kg (120-pound) person.
Throughout history, there has only been one documented case of toxicity.
One man drank too much of cinnamon whiskey whose contents included propylene glycol. He was found unconscious. Although most of the symptoms were due to the large alcohol intake, some of them could also be blamed on the propylene glycol.
In general, besides a single case of excessive consumption and other cases of allergies, no other cases of toxicity have been reported with regard to propylene glycol.
Since the current intakes of the chemical are way above the recommended levels, reducing dietary sources should be a priority, especially since processed foods are the primary sources of this chemical.
Propylene Glycol Health Effects
The dangers caused by propylene glycol are among the most highly contested topics about the chemical.
Some websites suggest that it is safe while others say that it is linked to conditions such as liver failure, heart attacks, brain problems and kidney failure.
How Toxic is This Chemical?
The level of toxicity of propylene glycol is very low. It has not been linked to problems such as cancer and damage of genes. Issues with reproduction and fertility have also not been associated with the chemical.
The median lethal dose of the compound in rats is 20 g/kg or 9 grams per pound. Sugar’s lethal dose, on the other hand, lies at 29.7 g/kg or 13.5 grams per pound. With salt, it is 3 g/kg or 1.4 grams per pound in rats. Once propylene glycol has been ingested into the body, approximately 45% of it is excreted unchanged, by the kidneys. The remaining amount is broken down into lactic acid in the body.
If it is consumed in toxic quantities, it may lead to lactic acid build-up, which will in turn cause kidney failure and acidosis. If the body cannot get rid of the acid faster than it is being formed, acidosis occurs. Proper functioning of the body is affected since the acid mainly builds up in the blood.
Depression of the central nervous system is the primary sign of toxicity. The symptoms will include loss of consciousness, slower breathing rate and a decrease in heart rate. Hemodialysis may be used to treat cases of poisoning. It removes the substance or drug that contains propylene glycol from the blood.
Cases of toxicity do not occur often, and when they do it is mainly due to ingestion of toxic levels or in some unusual cases. For instance, one man who had fallen ill drank what was contained in an ice pack.
Dangers for People with Liver or Kidney Disease
For adults who do not have any liver or kidney problems breaking down of and removal of propylene glycol from the body proceeds as usual, and also quite fast.
For people with the aforementioned problems, however, this process does not take place with as much efficiency. This may lead to excessive amounts of lactic acids in the blood which will consequently lead to toxicity symptoms.
In addition, the dosage of propylene glycol used in drugs has no upper limit. Therefore, it is quite possible to receive excessive doses of the chemical in some circumstances.
A certain who had kidney damage used lorazepam to treat throat swelling and shortness of breath. For a period of over 72 hours, she ingested over 40 times the recommended propylene glycol amount. This resulted in toxicity symptoms including acidosis.
Impaired liver and kidney function are prevalent in critically ill patients. The risk from high dosage or prolonged drug treatments is also high.
For instance, a particular study sings associated with propylene glycol toxicity were observed in 19% of patients who were being treated with lorazepam.
For people who have issues with their liver or kidney, drug alternatives that do not contain propylene glycol might come in handy when the need arises. Dietary amounts are not a cause for concern.
Dangers for Pregnant Women and Infants
Infants aged four and below, children and pregnant women all have low levels of an enzyme referred to as alcohol dehydrogenase. For propylene glycol to be broken down, this enzyme must be present.
These groups are, therefore, at a higher risk of showing toxicity if they ingest too much through medication.
Infants are at a higher risk than the rest. Their central nervous is more sensitive to effects than the rest and the process of removal of propylene glycol from their bodies takes three times longer than in the other groups. Some cases of infants who have been injected with vitamins that contain high amounts of the chemical have been reported. Seizures resulted from the high levels.
Another study, however, stated that young babies were able to tolerate, for over 24 hours, up to 34 mg/kg of propylene glycol.
Although these groups are at a higher risk of developing toxicity due to exposure to high levels from medication, evidence suggesting that amounts that are sourced from food are harmful does not exist.
Risk of Heart Attack
Some resources on the internet have claimed that propylene glycol is linked to heart attacks and diseases.
It is true that problems in heart rhythm and drops in blood pressure can occur if propylene glycol is injected quickly or in high amounts. Studies that were carried out on animals showed that some problems such as low blood pressure and a decreased heart rate may occur if propylene glycol is ingested in high amounts. The heart may even stop.
In a particular report, a child aged 8 months was treated with a cream referred to as silver sulfadiazine. It contained propylene glycol. The child later suffered from brain damage and loss of heart function. The cream was being used to treat burns that had covered 78%of his body.
For this particular case, the child received an excess amount of the chemical, that is 9 g/kg or 4.1 grams per pound.
In yet another case, a child age 15 months was given vitamin C that had been dissolved in propylene glycol. He later developed irregular heart rhythms and non-responsiveness, among other toxicity symptoms. He, however, recovered after stopping of the dosage.
These cases are doubtlessly concerning. However, it’s important to keep in mind that they both occurred from high dosages in an age group that it highly vulnerable.
Normal levels of propylene glycol in the diet are not linked to any heart problems.
Propylene glycol has been previously reported to cause brain-related problems.
In one case, a woman was poisoned with propylene glycol from an unknown source and she ended up developing stupor and repetitive convulsions.
Infants who were exposed to toxic levels of propylene glycol also developed seizures.
In a neurology clinic, 16 patients were given propylene glycol in measures of 887 mg/kg, thrice per day, for three consecutive days. One of the patients developed serious unspecified neurological symptoms.
In both of these studies, high amounts of propylene glycol were used. However, smaller doses in another study also found some effects.
Scientists observed that strange sensations, vertigo, and nausea were caused by 2-15 ml of propylene glycol. The symptoms, however, disappeared within 6 hours.
These symptoms may cause quite a scare in some people. Keep in mind that they can also be caused by taking many other medications in toxic amounts.
Once again, the amounts of propylene glycol in food have no association with neurological changes.
Skin and Allergic Reactions
According to the American Contact Dermatitis Society, propylene glycol is the 2018 allergen of the year.
In fact, about 0.8% to 3.5% of the population is estimated to be allergic to propylene glycol.
Dermatitis, which is the most common allergic reaction of the skin, is the development of a scattered pattern of a rash all over the body or on the face.
Taking medications and eating foods, as well as intravenous drugs, that contain propylene glycol has resulted in systemic dermatitis.
A study carried out on 38 highly sensitive people revealed that within 3 to 16 hours of oral ingestion of propylene glycol, 15 of them developed a rash.
Irritant contact dermatitis may also be caused by propylene glycol. In this case, sensitive people may develop a rash on their skin when they come into contact with products that contain propylene glycols such as moisturizer or shampoo.
People with skin conditions or those with sensitive skin are at a higher risk of developing a contact allergy to propylene glycol. It is important to avoid propylene glycol at all costs if you have allergic dermatitis. If you have contact dermatitis, stay away from products that contain propylene glycol and that come into contact with your skin.
The effects of inhaled propylene glycol to the body still remain unclear. It is important to make a distinction since this product is also used for theater productions in smoke machines as well as other inhalable substances. In rats, cells in the respiratory tract were enlarged and some nasal hemorrhaging occurred. The horse, that was previously mentioned, suffered from myocardial edema and eventually died due to respiratory arrest.
The information is relevant, even though the conditions under which the above events that happened are unlikely to happen in humans. Many substances can pose a serious danger when they are taken in toxic amounts. It’s also not possible to guarantee that this amount doesn’t build up to toxic levels, in some cases, especially.
Potentially Bioaccumulative in Specific Cases
Earlier in this article, I mentioned that propylene glycol is not bioaccumulative, (builds up in the bloodstream with time.) Critically ill adults are, however, an exception. Whether or not they had kidney issues, adults who ingested high amounts of lorazepam showed an abnormal accumulation of propylene glycol.
If you are critically ill, or if you have issues with your kidney or liver that are likely to affect processing of organic compounds by your body, I strongly recommend that you stay away from propylene glycol as much as possible. Propylene glycol may prove to be a chemical to these individuals.
In a cases study, a 24-year old woman suffering from pneumonia used lorazepam for 18 days in an attempt to treat her dangerous respiratory disorder, during that period she developed lactic acidosis, a condition in which the body’s pH level drops to a dangerous extreme. Her condition stabilized for a while after she stopped taking the medication that had caused the problems. She, however, later died when her health deteriorated once again. Once more, this is just an example of the possible, but rare, consequences of accumulation of propylene glycol in our bodies.
How to Avoid Propylene Glycol
Though this compound is considered safe, you may want to avoid it if you want to reduce your intake or if you are allergic to it.
You can check its presence by reading the ingredient’s list of food products. The following names may be used to describe it:
- Propylene glycol
- Propylene glycol mono and diester
- E1520 or 1520
If the compound has been used as a solvent for other products such as color or flavor, instead of being used as a direct ingredient, or as a carrier, it will not appear in the ingredients list.
It is mainly found in junk foods that have been highly processed. Therefore, if you eat a fresh diet, with whole foods, you will be able to avoid it without going through much trouble.
If you use cosmetic produces, avoiding it might prove to be difficult. There is a list of some websites which might help you identify the products that do not contain it.
If you are allergic to propylene glycol, it is highly important that you let your pharmacist or doctor know about your condition before you start taking any medications. You may find an alternative together.
Propylene glycol is a very useful product that is found in a wide range of products in industries such as the drug, cosmetic, food as well as the manufacturing industry. Even though there are some reported cases of toxicity that occur from ingestion of high doses of medication, propylene glycol is widely considered as a safe product that’s very low in toxicity levels.
A small percentage of the population is allergic to this product and they may need to stay away from products whose contents include propylene glycol. For most people, the amounts of propylene glycol found in foods do not pose any danger to them.
Always remember that propylene glycol is mainly found in junk foods that are highly processed. A healthy, whole food diet will contain very small amounts of this chemical product.
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